RAID is a technology that employs the simultaneous use of two or more hard disk drives to achieve greater levels of performance, reliability, and/or larger data volume sizes. RAID is now used as an umbrella term for computer data storage schemes that can divide and replicate data among hard disk drives. Various designs involve the design goals of increased data reliability and increased input/output performance. When several physical disks are set up to use RAID, they are said to be in a RAID array. The RAID array distributes data across several disks, but the user and operating system see the array as one single disk. RAID can be configured in various ways to serve different purposes.
Many RAID arrays, due to budget limitations and/or hardware limitations, are configured asymmetrically (i.e. have a different number of disks feeding the RAID card channels). This can lead to an imbalance in the underlying RAID configuration and an inability to fully service the RAID card channel(s) under a given I/O load. The only currently known solution is to leave the RAID array unbalanced or to purchase additional hardware.
Accordingly, a need has arisen to provide proper load balancing to maximize asymmetric RAID configurations.